Use Basic/Digest Auth from Requests

As suggested in #52
Original auth mechanism introduced in #27
This change should retain backwards compability
Remove deps no longer used
Fix so maxlag is handled correctly

- If database lag exceeds max lag, the API will still send 200, not 503.
  This was only added to documentation after bugzilla:31156.
  Ref. <https://www.mediawiki.org/wiki/Manual:Maxlag_parameter>
- In addition, Requests doesn't raise an exception when status code != 200
  unless raise_for_status() is called, so we should call that to catch
  any other 5xx errors such as Squid errors.
- Replace print statements with logging

Note that responses>=0.3.0 is needed to run the test suite now
Merge remote-tracking branch 'origin/master'

Conflicts:
	RELEASE-NOTES.md
[#52] Use Python 3.x compatible exception handling

Back-ported to Python 2.6 and 2.7
[#52] Use print function and Py3.x compat methods

Prepare for Python 3.x support
- Use print function
- Use compability methods from six